One sort of tubular netting of thermoplastic material which may be used to make the product of the present invention also is the raw material for the process described in the patent of Kebekus, et al, U.S. Pat. No. 3,017,314, issued Jan. 16, 1962. In Kebekus, et al, the netting is advanced through a work station where it is radially constricted at two axially slightly spaced points and periodically is simultaneously heat welded and severed between these two points, then cooled--thus adjacently making the bottoms of what is to become two bags.
A recently issued patent of Pelster, et al, U.S. Pat. No. 4,091,595, issued May 30, 1978 shows a manufacture at the bag filling station, of plastic netting bags made from the preferred material, Dupont's Vexar plastic mesh tubing.
Although the resulting kind of bag has myriad uses, presently it is best known to most consumers as the plastic netting bag in which grapes, oranges, onions and the like often are sold in supermarkets. Marbles are typical of a non-food product which can be packaged in similar material. This kind of bag is in increasing demand for use in place of plastic film bags, for packaging products which do not require envelopment by a complete vapor barrier.
A further use is to permit foodstuffs and the like to be soaked in a processing fluid while individual quanta thereof are segregated into individual fluid-permeable packages. Typical is the marination of pre-sorted, pre-selected amounts of cut-up chickens, e.g. the whole or a proportional amount of the cut-up chicken which will be cooked in the same batch at a fast food retail store which features fried chicken.
In small-scale packaging operations, individual bags such as are produced using hot knife thermal welding with simultaneous bag cut-off, are conveniently used. With larger scale operations, particularly for use with produce-bagging machinery which is at least partially automated, often the most efficiently useful product is a continuous "rope" of potential netting bags produced by gathering and sealing the netting strands every so often along the length of the rope. The rope can be payed off a roll and successively cut through next to each seal to successively make individual bags. In other words, for such a product, severing operation is not performed simultaneously with the gathering and sealing, and may be performed, e.g. by a customer at a field location, rather than by the manufacturing entity which made the intermittantly sealed rope. Further, the spooled, intermittantly sealed rope of tubular thermoplastic netting material may serve as a supply of bags to an automated bagging machine (not part of the present invention) which successively pays out, fills, closes and severs the leading bag of the rope. A similarly desirable product is a boxed coil of such rope of bag precursors in series. Another, is a transparent package of a plurality of individual, empty bags. The package having a grab-hole in its side wall through which the bags may be individually withdrawn for filling.
Paxton, U.S. Pat. No. 3,732,662, issued May 15, 1973 shows packaging goods into tubular netting using a "sausage-stuffing" technique. When the tube terminal portion holds a full quantum of goods, it is manually spun, mechanically clamped, and cut off.
Herrell, U.S. Pat. No. 3,780,488, issued Dec. 25, 1973 shows that it is known to seal a non-twisted, tubular thermoplastic film, simply gathered and clamped between an ultrasonic horn and anvil to form a package end.
It has been found that if one radially gatheringly condenses a tube of thermoplastic netting and attempts to make a seal using an ultrasonic horn and anvil, quite commonly two, three or several separate seal nuggets and sometimes a fray are formed. These are not integrated into a separate seal and results in bags having one or more weak sections or gaps in their bottoms. While, but for having an undesirably nonuniform appearance, such bags could be used to package larger items, such as large onions, which are not likely to fall out through small gaps in the bag bottom, these bags cannot be used to reliably package small items such as grapes or marbles.